sectionLabel formatting

[Stu McKenzie]

The Notation Reference document for version 2.25.19 has a simple example 
on page 292:

\fixed c' {
\sectionLabel "Verse"
c2 g
\section
\sectionLabel "Chorus"
g2 c
\bar "|."
}

The Notation Reference states on the same page:
"Before using text marks, it is recommended to seek a more specific 
command, if available.
For text that identifies a section, use \sectionLabel (see [Section 
labels], page 292)."

All sectionLabel examples in the Reference have no formatting.

I'd like to format the sectionLabel.

I know that I can format a \textMark with e.g.:
\textMark \markup { \box \bold "Chorus" }

Is there a way to format sectionLabel, or is textMark (or something 
else) required instead?